Project Summary/Abstract Millions of US adolescents are chronically sleep-deprived during a developmentally critical period, when the proximal effects of sleep deprivation may have serious long-term consequences. Although inadequate sleep during adolescence has been associated with poor health outcomes, the conclusions that can be drawn from prior studies are limited by their correlational nature. A few experimental studies have shown that sleep- deprived adolescents fall asleep easily, but this accounts for only one of the suspected effects of sleep deprivation on behavior and does not address effects on brain functioning. Experimental studies from other developmental periods have suggested that inadequate sleep alters brain activity and causes behavioral deficits, most prominently inattention. However, findings from young children are too incomplete, relate to demands that are too different, and are based upon a sleep physiology that is too dissimilar, to be extrapolated to adolescents. Similarly, adult findings lack ecological (real world) validity when applied to adolescents and do not take into account developmental factors. The field lacks developmentally-appropriate experimental work that conclusively determines whether and how inadequate sleep alters adolescents' neural and neurobehavioral functioning. This has limited the conclusions one can draw about the effects that chronic sleep restriction has on adolescents and has slowed public health initiatives to improve adolescent sleep. The overall goal of our multidisciplinary research program is to advance science and promote public health by clarifying the proximal and distal effects of inadequate sleep during adolescence. To complement and inform the longitudinal work on distal effects that is underway and planned through our program, the current study will examine the proximal impact of experimental sleep restriction on healthy adolescents' neural and behavioral functioning, focusing on the fundamental neurobehavioral system of sustained attention. 100 adolescents will undergo a within-subjects randomized crossover protocol that includes five nights in a sleep deprivation condition (SD; 6.5 hours in bed with lights out) and five in an healthy duration condition (HD;10 hours with lights out), followed by morning assessments at the end of each week. The central hypothesis is that, relative to the HD condition, adolescents in the SD condition will display attention deficits that will be reflected in direct assessments of neural functioning (EEG and fMRI) and in behavioral measures. This study aims to determine (1) the proximal impact of sleep restriction on adolescents' neurobehavioral functioning, (2) the impact of sleep restriction on adolescents' brain functioning while they are engaged in sustained attention tasks, and (3) the relationship between neural state and neurobehavioral performance in sleep-deprived adolescents. In achieving these aims, this study will determine the impact of chronic sleep restriction on important aspects of the daily functioning of adolescents, and gain new insight into the neural mechanisms that underlie this impact.